According to Baidu Encyclopedia, "Mulan joined the army as her father in ancient times, and now female soldiers carry guns for the people" comes from the lyrics in "Liege of Female Soldiers", which is the theme song of China's modern ballet "The Red Female Soldiers".

On September 26th, 1964, the ballet "The Red Female Soldier" officially premiered in the small auditorium of the Great Hall of the People. For more than half a century, Liege of Female Soldiers has been powerful and inspiring, and spread all over the country. This is a classic revolutionary song.